1. Field of the Invention
The present invention relates generally to a method for forming a capacitor of a semiconductor device, and more particularly to a method for forming a capacitor of a semiconductor device, which can improve a leakage current characteristic of HfO2 applied as a dielectric film of the capacitor by suppressing low-temperature crystallization thereof.
2. Description of the Prior Art
Recently, cells of a DRAM device has occupied a smaller area with increase in a degree of integration of the DRAM device, so it becomes more and more difficult to ensure charging capacity required. As is well known in the art, the charging capacity of a capacitor is proportional to an area of an electrode and a dielectric constant of a dielectric film, and is inversely proportional to a distance between electrodes, that is, a thickness of the dielectric film. For ensuring charging capacity required, therefore, it is necessary to reduce the thickness of the dielectric film or to apply materials having a large dielectric constant as the dielectric film.
Thereupon, in order to ensure charging capacity required, researches are being vigorously pursued to replace the existing Oxide-Nitride-Oxide (ONO) dielectric film by a single dielectric film of Al2O3 (ε=9), a single dielectric film of HfO2 (ε=20) or a dual dielectric film of simply laminated HfO2/Al2O3.
However, Al2O3 has a restriction on ensuring charging capacity because its dielectric constant is not so different from that of the existing Si3N4 material (ε=7), and HfO2 has a poor leakage current characteristic caused by a low crystallization temperature although it has a large dielectric constant. The dual dielectric film of HfO2/Al2O3 also has a limitation on reducing an equivalent oxide thickness (EOT; Tox) due to the small dielectric constant of Al2O3.
In the end, the single dielectric film structure of Al2O3 or HfO2 and the dual dielectric film structure of HfO2/Al2O3 may ensure charging capacity required for a capacitor of a highly integrated device such as a 65 nm-grade device, but cannot satisfy the leakage current characteristic of the capacitor. Consequently, the development of a dielectric film applicable to the 65 nm-grade device must be settled without delay.